An optical apparatus such as a digital still camera or a video camera for capturing subject images by using a solid-state imaging device such as CCD and CMOS has generally equipped with a zoom lens.
However, in most zoom lenses, as the focal length in the telephoto end state becomes longer, an outer diameter of the lens in the most object side lens group becomes large as well as the total lens length becomes long, as a result the lens barrel becomes large causing a problem in portability.
In order to increase portability, each lens group is accommodated in the camera body such that each distance between lens groups are narrowed to become minimum upon carrying a digital still camera.
Moreover, in order to make the thickness of the camera body thin, the lens barrel is composed of partial lens barrels and the length of each partial lens barrels is shortened. However, it is impossible that the thickness of the camera is thinner than the length of each partial lens barrel.
Nowadays portability upon carrying a digital still camera is considered to be most important, so that in order to make a camera body compact, thin, and light, a zoom lens as an image-taking lens is made to be compact and light.
Then, there has been devised a zoom lens in which an optical element capable of bending an optical path substantially 90 degrees is included in a portion of lens group thereof. With equipping such a zoom lens, upon moving from an accommodating state to a using state, lens groups do not protrude from the camera body, so that excellent portability is secured in the using state. Moreover, it greatly contributes for making the camera compact and thin. Furthermore, since moving elements are disposed in the camera body, and no moving elements exist on the surface of the camera body, it is effectively used for various purposes such as waterproof, drip-proof, dustproof, and the like.
There has been proposed a positive-negative-positive-positive, four-lens-group type zoom lens that is capable of bending an optical path, and composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power in such as Japanese Patent Application Laid-Open Nos. 2003-302576 and 2004-264585.
Although the one disclosed in Japanese Patent Application Laid-Open No. 2003-302576 contributes to be compact by effectively varying distances between the second lens group, the third lens group and the fourth lens group upon zooming, since three lens groups have to be moved, there is a problem that the moving mechanism becomes complicated.
In a zoom lens disclosed in Japanese Patent Application Laid-Open No. 2004-264585, there is a problem that imaging performance deteriorates by an image blur caused by a camera shake happened upon depressing a shutter release button by a user. Accordingly, there has long been desired a zoom lens having a vibration reduction function for correcting an image blur on the image plane by shifting a portion of the optical system of the zoom lens substantially perpendicular to the optical axis on the basis of an output of a detector for detecting a camera shake.